The present invention relates to a gas bag module comprising a housing, an inflator arranged on the bottom of the housing, a folded gas bag behind a cover closing off the housing and a diffusor between the inflator and the folded gas bag.
In most prior art gas bag modules the gas bag wall is directly exposed to hot gas produced by a pyrotechnic inflator to inflate the gas bag. The module generally comprises a door hinged to an edge of the module housing remote from its bottom, and normally covering the folded gas bag to retain it within the module housing in the folded condition. When the gas bag is inflated, it urges against the door which swings open so that the gas bag is free to deploy. In some prior art gas bag modules a diffusor is arranged between the folded gas bag and the inflator to provide for a distributed and controlled flow of gas into the gas bag.
The present invention provides a gas bag module that enables an improved gas bag deployment and a controlled flow of gas from the inflator into the gas bag upon inflation.
According to the invention, a gas bag module is provided that comprises a housing with a bottom, an inflator arranged on the bottom of the housing, a folded gas bag and a diffusor between the inflator and the folded gas bag. The diffusor consists of a first diffusor part fixed to the bottom of the housing and a second diffusor part movably mounted on the first diffusor part. The second diffusor part is movable with respect to the first diffusor part from a normal retracted position closer to the bottom of the housing to an advanced position further away from the bottom of the housing under the action of gas pressure generated by the inflator. In a first embodiment of the invention, the second, movable diffusor part on movement from the retracted to the advanced position, pushes the folded gas bag package out of the housing prior to inflation of the gas bag, thereby permitting the gas bag to deploy in preferred directions. In a second embodiment where the gas bag module has a hinged door covering the folded gas bag, the second, movable diffusor part on activation of the inflator is first exposed to gas pressure, then urges against the cover to swing it open, moves to its advanced position and only then permits gas to flow into the gas bag for inflation. Since the door is open prior to actual inflation of the gas bag, an improved control of gas bag deployment is achieved.